

Apple directly makes money off iOS apps and in most of the world you can only buy via their store. On the other hand, I can and do buy games from GoG and run them just fine on my Steam deck and can still benefit from proton.
The only reason I buy most of my games from Steam is they make things even easier than buying from GoG.

Epic doesn’t do a single thing that doesn’t directly result in profits. Features are only added off they can derive income from them. Lawsuits are filed so they can take a larger percentage of profits. Even his twitter posts are mainly about him getting a larger cut, when he isn’t defending AI child porn.
Valve is very old school in their ‘keep improving your offering and it will work out’ way. Usually companies like that get bought out and their name run into the ground. It sadly happens in all industries, from Samsonite luggage to BioWare games and even service companies.